The corneal endothelium of the adult human possesses essentially no regenerative capability; typically, in vivo cell loss is followed by compensatory hypertrophy of the remaining endothelium. This lack of regenerative capacity poses a significant clinical problem, as many corneal diseases are accompanined by endothelial cell loss, resulting in corneal edema. Additionally, certain ophthalmic surgical procedures are associated with significant losses of endothelial cells: penetrating keratoplasty, cataract extraction, and intraocular lens implantation. In most instances, patients with significant corneal edema, secondary to low endothelial cell densities (or endothelial dysfunction) need only have the endothelium replaced to restore corneal clarity. Currently, medical management of endothelial cell loss is limited to penetrating keratoplasty. The establishment of human corneal endothelium in tissue culture and subsequent transplantation to denuded Descemet's membrane, yielding a monolayer of functionally intact cells, would be a breakthrough of major importance. Prolonged cultures of human neonatal corneal endothelium with demonstrated adherence to human corneal buttons denuded of their native endothelium is currently being achieved. So as to evaluate the long term viability and functional integrity of cultured human corneal endothelium in vivo, and provide preliminary data to assess the effectiveness and reproducibility of this approach, a series of experiments have been designed involving transplantation of cultured corneal endothelium into rhesus. Group I will consist of xenografts (human buttons into rhesus) and serve as control for surgical technique. Group II will consist of xenografts lacking endothelium and will serve to confirm the extent of recepient endothelial growth and migration. Group III will consist of xenografts with transplanted corneal endothelium. Clinical evaluation (biomicroscopy, wide-field specular microscopy, tonometry, and pachymetry) will assess the functional integrity of the transplanted endothelium; cell morphology will also be evaluated, as determined by scanning electron microscopy. It is anticipated that the results of these experiments will illuminate the functional status of transplanted endothelial cells, in vivo, and provide pilot data indicating the feasibility of this project on a larger scale.